Many plug-in hybrid electric vehicles (PHEVs) have two electric motors. One motor may typically be utilized for traction while the other is utilized for power generation. There are also other accessory electric motors in these vehicles (i.e., air conditioning compressor, and power steering pump). These motors are often three-phase permanent magnet motors, which, during operation are powered by an on-board power supply, such as a battery. As the vehicle is operated, the on-board power supply discharges and requires recharging at some point.
The PHEVs have on-board power generation capabilities using a fuel based generator to partially recharge the on-board electrical power supply as needed. However, it may be preferred to recharge the on-board power supply using an external power source when possible.
For opportunistic recharging using an external power source, it is beneficial for the vehicle to have the ability to accept power from any standard electrical outlet and Electric Vehicle Support Equipment (EVSE) and possibly a DC source. Electronics associated with such opportunistic recharging may undesirably add cost and/or weight to the vehicle. Since it may not be practical to plug-in charge and drive the vehicle at the same time, dual purposing the drive magnetics and power electronics and/or the accessory motor systems as part of the battery charger may be utilized.
For example, the battery charger may be integrated into a dual three-phase motor drive train with star connected motor windings by connecting a plug-in power supply to the neutral node of each three-phase motor.
With the neutral node connected configuration, equal currents can be made to flow through the motor windings to avoid creating motor torque. When equal currents are caused to flow through three-phase windings of the motor, however, what can be utilized is only the leakage inductance of the windings. Therefore, there may be problems that the commercial power supply cannot sufficiently be boosted to the battery voltage, or influence of ripple to the input side increases.
Further, when single-phase or dual-phase motor windings are selected and a current is caused to flow therein to utilize the higher magnetic inductance, the motor generates torque which could cause the vehicle to move or oscillate during charging especially as the stator winding current changes direction each AC half line cycle.
Further, these neutral node connected integrated charging systems tend to induce a high common-mode noise, electromagnetic interference (EMI), and unwanted ground currents.